Apparatus and method for masking display element defects in a display device

ABSTRACT

The invention is directed towards an apparatus and method for masking display element defects in a display device. In one embodiment, the invention includes a display device with display elements disposed on a display surface, a translation unit that is coupled to the display device to impart periodic motion to the display surface, a display signal source capable of providing input signals to the display device, and a control unit coupled to the translation unit and the signal source to direct the movement of the display device and the signal source to correspondingly shift the display signals, which when displayed, conceal display element defects while presenting a stable image to a stationary viewer.

TECHNICAL FIELD

[0001] This invention relates generally to display devices, and moreparticularly, to a method of concealing display element defects in adisplay device.

BACKGROUND OF THE INVENTION

[0002] Various types of visual display devices are in widespread use toconvert electrical signals into visual imagery. For example, there areemissive displays such as cathode ray tubes (CRT), light-emitting diode(LED) displays, field emission displays (FED), and gas discharge(plasma) displays. There are also non-emissive displays, such as liquidcrystal displays (LCD), electrochromatic displays and electrocolloidaldisplays. The following discussion applies to all of these types ofdisplays.

[0003] In a visual display device, the image is generally formed on adisplay surface of the device by selectively stimulating, throughelectronic means, discrete elements positioned on the display surface.The discrete display elements vary in light intensity and/or color inresponse to the applied electrical stimulation so that a plurality ofadjoining areas of differing light intensity and/or color are obtainedon the display surface. In particular, when the display elements arevery small in comparison to the size of the display surface, a viewer ofthe display screen perceives a continuous image.

[0004] An active matrix liquid crystal display (LCD) is a good exampleof the utility of this display technology. The LCD generally includes apair of opposed glass substrates that are bonded together to form anenclosed volume that is filled with a liquid crystal material. Theinterior surface of one of the substrates is continuously coated with alayer of a conductive material to form a display surface, while theinterior surface of the opposing substrate is patterned into individualdisplay element electrodes that are arranged in a matrix fashion.Associated with each display element electrode is a switching element,generally comprised of a Thin Film Transistor, or a Metal InsulatorMetal diode. Selection or non-selection of the display elements isachieved by the switching operation of the switching elements to makethe display operable. A back lighting system is generally located behindthe substrate opposite the display surface to transmit light through thesubstrates and the liquid crystal material so that a luminous display isvisible to the user.

[0005] Most commonly, two display modes are used in active matrix LCDdisplays. In the “normally black” mode, the back lighting system isshielded from the viewer by the liquid crystal when no signal is appliedto a display element electrode. When a signal is applied to the displayelement electrode, light is transmitted through the display element, andis perceived by the viewer as an illuminated area. An alternative mode,referred to as the “normally white” mode, allows light to be transmittedwhen no signal is applied to the display element electrode, andcorrespondingly shields the back lighting system when a signal isapplied to the display element electrode.

[0006] The switching elements, display element electrodes, andinterconnections are generally patterned onto the substrate usingwell-known semiconductor fabrication methods to achieve a complexmultilayered structure consisting of layers of semiconductor materials,insulating materials, and various types of metals. Although thefrequency of fabrication defects occurring in the formation of theelements, electrodes, and interconnections is generally low, when anactive matrix LCD includes several hundred thousand display elements,the probability that numerous switching devices, electrodes, and/orinterconnections on the substrate will be abnormally formed is notinsignificant. Consequently, the display elements associated with thesedefective structures will not operate as intended, and are generallyperceived by the user as a display element that exhibits a constantwhite condition, or conversely, a constant black condition, depending onthe mode of operation of the display. The presence of the foregoingdisplay element defects may therefore degrade the image formingcapability of the visual display to the point that it is unacceptablefor end-use.

[0007] Presently, the high yield production of active matrix LCDswithout display element defects presents a significant technicalchallenge. In general, displays are fabricated with some acceptablenumber of defects, which are corrected through the application ofvarious techniques, in order to improve the yield of acceptabledisplays. In low-resolution displays, the usual yield inhibitor is thepresence of only a moderate number of individual display elementdefects. In higher resolution arrays, where the contribution of anindividual display element to the overall image is much lesssignificant, the presence of array-line defects is of principal concern.Accordingly, considerable effort has been directed towards thedevelopment of techniques to correct or conceal display element defectsof these types in order to salvage defective displays.

[0008] The correction of individual display element defects in activematrix LCD displays has received considerable attention. For example,U.S. Pat. No. 5,638,199 to Tsubota, et al. describes a repair method fora defective “bright spot” display element whereby a photosensitiveresist is applied to the substrate on the display side of the device,followed by the projection of a light source through the display whileall of the display elements in the display are activated. Locations inthe display where the light projects through the display thereforecorrespond to defective display elements, and exposure of thephotosensitive resist to the light source occurs at these locations.Upon development of the resist, an opaque layer is formed that concealsthe “bright spot” defect. A particular shortcoming of this technique isthat it introduces several new steps in the display fabricationprocedure, and accomplishes only the opaque masking of “bright spot”defects.

[0009] Other prior art methods selectively alter the structure of thesubstrate surface in order to reorient the liquid crystal molecules sothat a display element defect is concealed. For example, U.S. Pat. No.5,926,246 to Tomita, et al. describes a method where the aligning filmin a defective display element is irradiated by a laser to form minutegrooves oriented in a direction that differs from the grooves that wereoriginally present on the aligning film. As a result, the twistorientation of the liquid crystal molecule is altered, so that the lighttransmission qualities of the display element are permanently altered,thus making a “bright spot” defect in the display less conspicuous. Asimilar method is described in U.S. Pat. No. 5,636,042 to Nakamura, etal., wherein a series of randomly oriented grooves are formed on thealigning film by irradiation of the defective display element by alaser. The random aligning grooves permit the liquid crystal moleculesto be oriented with a plurality of different twists and orientationsthereby achieving an overall muting of a “bright spot” defect.

[0010] A significant shortcoming present in the foregoing methods isthat the defective “bright spot” pixel must be individually corrected byselectively forming new aligning grooves in the aligning film to achievethe desired attenuation in illumination level. In a display containing alarge number of display elements, correction of even a modest number ofdefective display elements will be a time consuming task, renderingthese methods suitable for salvaging defective displays with only smallnumbers of display element defects.

[0011] Still other prior art methods seek to minimize the occurrence ofdefective display elements by providing redundant components duringfabrication of the display. These prior art methods are directed inparticular towards the correction of array-line defects referred toearlier. For example, U.S. Pat. No. 5,490,002 to Nicholas describes anactive matrix device that uses two parallel-connected switching elementsto provide fault tolerance in the event that a switching element isabnormally formed as an open circuit, while allowing a short circuiteddevice to be removed by selective laser scribing.

[0012] These prior art methods have the disadvantage of requiring theselective correction of individual defective display elements throughthe application of laser scribing techniques to activate the redundantcomponents, and to deactivate the defective components, which limits thepractical applicability of such methods to displays with a small numberof display element defects. Additionally, these methods may not correctinstances where the display element failure has resulted from thefailure to properly form other essential components of the displayelement, such as the electrode, or other interconnections, since thesemethods generally contemplate the failure of switching components only.

SUMMARY OF THE INVENTION

[0013] The invention is directed towards apparatus and methods formasking display element defects in a display device. In one aspect, anapparatus in accordance with the invention includes a display devicethat includes a plurality of display elements disposed on a displaysurface, at least one display element being at least partiallydefective, a translation unit that is coupled to the display device thatis structured to impart a periodic motion to the display surface, adisplay signal source capable of providing input signals to the displaydevice, and a control unit that is coupled to the translation unit andthe signal source that controllably directs the movement of the displaydevice and controllably directs the signal source to correspondinglyshift the display signals. The shifted display signals, when displayed,conceal display element defects while presenting a stable image to astationary viewer. In another aspect of the invention, the display unitis comprised of horizontal and vertical linear supports that permit thetranslation unit to translate the display in horizontal and verticaldirections, the control unit is further comprised of horizontal andvertical actuators, and the control unit is further comprised ofhorizontal and vertical position sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a frontal view of a display surface showing a group ofdisplay elements on the display surface.

[0015]FIG. 2 is an enlarged view of a portion of the display surfaceshowing display elements and image areas on the display surface.

[0016]FIG. 3 is an enlarged view of a portion of the display surfaceshowing the physical shifting of the display elements and the shiftingof the image areas.

[0017]FIG. 4 is a flowchart of a method of masking defective displayelements according to an embodiment of the invention.

[0018]FIG. 5 is a schematic view of an apparatus for masking defectivedisplay elements according to an embodiment of the invention.

[0019]FIG. 6 is a schematic view of an apparatus for masking defectivedisplay elements according to another embodiment of the invention.

[0020]FIG. 7 is a schematic view of an apparatus for masking defectivedisplay elements according to an alternative embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention is generally directed to an apparatus andmethod for masking defective display elements in a visual displaydevice. Many of the specific details of certain embodiments of theinvention are set forth in the following description and in FIGS. 1through 7 to provide a thorough understanding of such embodiments. Oneskilled in the art will understand, however, that the present inventionmay have additional embodiments, or that the present invention may bepracticed without several of the details described in the followingdescription. For example, the embodiments of the invention as discussedbelow disclose motion of the display surface along twomutually-orthogonal axes. It is understood, however, that the presentinvention may include movement of the display surface along a third axisthat is mutually orthogonal to the two axes described in connection withthe disclosed embodiments. Further, it is understood that the displaysurface may be moved relative to a non-orthogonal axis system, or may berotated and/or translated relative to a polar coordinate system. Oneskilled in the art would possess the ability to practice the disclosedinvention with a motion along a third axis, or with motions relative toa non-orthogonal system without undue experimentation.

[0022]FIG. 1 shows a frontal view of a display surface 10 that iscomprised of an array of individual display elements 14. For clarity,the display elements 14 are shown only for a selected surface region 11on the display surface 10. One skilled in the art will understand,however, that the display elements 14 are generally arranged into aknown number of horizontal rows 12 and vertical columns 13 tosubstantially occupy the entire viewing area of the display surface 10.Further, it is understood that the display elements 14 may include asingle display element, or may be comprised of a larger group, orsubgroups of contiguous display elements. Moreover, one skilled in theart will understand that in foregoing description, picture elements, orpixels, generally correspond to the image elements described herein.Additionally, the display surface 10 may be comprised of any of thedisplay technologies previously discussed.

[0023] Turning now to FIG. 2, an enlarged view of the selected surfaceregion 11 of a display surface is shown, which depicts in greater detailthe features present in the surface region 11. The following discussionwill be limited to a small group of display areas on the display surfaceto better illustrate the disclosed apparatus and method, and ispresented for purposes of description only. One skilled in the art willunderstand that the disclosed apparatus and method may be extended tothe entire display surface 10, as shown in FIG. 1.

[0024] Still referring to FIG. 2, the region 11 shows adjoining displayelements 20-31 that correspond to physical areas on the display surface10. Associated with the display elements 20-31 are image elementsP₂₀-P₃₁ that are individually projected onto the region 11 by the imagesignals V₂₀-V₃₁ to create an image, or a portion of an image, that maybe visually perceived. As previously discussed, the image elementsP₂₀-P₃₁, produced by the image signals V₂₀-V₃₁ may be created byemitting light, or by causing a change in the light transmissioncharacteristics of the display elements 20-31 or by still other means tovisually convey the information associated with the image signalsV₂₀-V₃₁ to a viewer.

[0025]FIG. 2 further shows the display elements 20-31 on the region 11arranged into rows 35-37, and columns 38-41, as shown. For purposes ofdescription, a single display element 25 that is located in the region11 is at least partially unresponsive to the applied input signal V₂₅,while display elements 20-23, 24, 26, 27 and 28-31 are filly responsiveto the image signals V₂₀-V₂₃, V₂₄, V₂₆, V₂₇ and V₂₈-V₃₁, and thereforefunction normally. The defect that exists at the display element 25 mayexhibit constant illumination, partial illumination, or no illumination,depending on the display technology used, and the particular mode offailure. Due to the defect in the display element 25, the image elementP₂₅ associated with the image signal V₂₅ does not fully appear in thedisplay element 25.

[0026]FIG. 3 shows the region 11 with the single defective displayelement 25 after the region 11 has been physically translated a distanceof one column width to the left. The apparatus for accomplishing thephysical translation of the region 11 will be more fully discussedbelow. In response to the physical translation of the region 11 to theleft, the image elements P₂₀-P₃₁ must be simultaneously translated acorresponding distance to the right, which is accomplished byredirecting the image signals V₂₀ -V₃₁ one column width to the right inorder for the image to appear untranslated on the region 11 with respectto a viewer. As a result, the information that was previously associatedwith the input signal V₂₅ that could not be fully viewed because theimage element P₂₅ coincided with a defective display element 25, is nowviewed in display element 26. At the same time, although the region 11has been translated by the width of one column, the image element P₂₅has maintained a position that is unchanged relative to a viewer of theregion 11. After all of the image elements P₂₀-P₃, have been displayedby the redirected image signals V₂₀ V₃₁, the region 11 is physicallytranslated one column width to the right so that the image elementsP₂₀-P₃₁ are projected onto display elements 20-31 as initiallypositioned and shown in FIG. 2, whereupon the image is displayed again.

[0027] With reference now to FIG. 4, a method for recursivelyimplementing the procedure previously described is shown. At step 45,all of the display elements on the display surface are physicallytranslated a known distance, either vertically and/or horizontally withrespect to a stationary viewer. If display element defects areessentially unitary and widely dispersed across the area of the displaysurface, movement in either the horizontal direction, as described withreference to FIGS. 2 and 3, or in a vertical direction may be used toequal advantage. However, if the display element defect extends acrossthe display surface in a predominant direction, physical translation ofthe display areas in a direction substantially perpendicular to thepredominant direction may be preferred. For example, active matrixliquid crystal displays are subject to fabrication defects thatgenerally result in the loss of at least a portion of a row of displayelements on the display surface. In masking a defect of this type, avertical movement of the display would be favored, as opposed tohorizontal movement, since the defective display elements that extendalong a substantial portion of the row length are too distant from othernon-defective display elements present in the same row. In contrast,physically translating the defective display elements in the row in avertical direction would have the advantageous effect of using thefunctioning display elements located immediately above or below thenon-functioning row. Alternatively, a combination of horizontal andvertical physical translations could be employed to mask a defect ofthis type.

[0028] The distribution of the defective display elements present in thedisplay may be ascertained prior to the formulation of the path forphysically translating the display. For example, if the display defectsare preponderantly row defects, then a generally vertical translationwill be effective in masking these defects, as described above. However,if the defects consist predominantly of contiguous display elements,then a combination of horizontal and vertical translations and/ortranslations through more than a single display element width might bemost effective in concealing these defects. The distribution of defectsin the display may be conveniently assessed by simultaneously providinga uniform input signal to each display element, and visually assessingthe distribution of defects on the display surface.

[0029] Still referring to FIG. 4, step 46 requires that the imageelements be moved a distance that equals the physical translationdistance of step 45, but in the opposing direction, so that the positionof the respective image elements remains stationary with respect to theviewer. As previously described, the translation of the image elementsoccurs by redirecting the corresponding image signals to differentdisplay elements. At step 47, the shifted image is displayed to theviewer, by the well-known methods of raster scanning, or by matrixaddressing the discrete elements in the display surface. After theshifted image is displayed, the display elements may be physicallytranslated back to their respective initial positions by returning tostep 45. Alternatively, the display may be physically translated instill another direction at step 45, to conceal other defects, beforereturning to the initial display position.

[0030] The repetitive physical movement of the display elements whencombined with the corresponding shift in the images being displayedpresents to a viewer the perception of a complete image on the displaysurface 10 (as shown in FIG. 1). This has the advantageous effect ofallowing the image associated with the defective display element to beintermittently viewed by periodically shifting the image away from thedefective display element. If the periodic shifting of the displayelements occurs with sufficient rapidity, the intermittency of the imageobtained thereby will become less apparent to the viewer, who willperceive a stable, non-flickering image. Since it is well establishedthat intermittent imagery presented to a human viewer appears to becontinuous if the frequency of repetition is greater than about 50 Hz,it follows that if the display elements are physically translated atapproximately this frequency, a continuous image will be perceived bythe viewer. Although the foregoing discussion has disclosed movement ofthe display in horizontal and/or vertical directions, it is understoodthat the display may be moved in a third direction that is orthogonal tothe horizontal and vertical directions.

[0031] Turning now to FIG. 5, a schematic view of an apparatus 50 formasking defective display elements according to an embodiment of theinvention is shown. As shown therein, a visual display 62 having afrontally disposed display surface 64 is positioned within the field ofview of a viewer (not shown). While the display 62 may be comprised ofany of the display devices previously discussed, the display 62 is aflat panel display with low mass. The display 62 is coupled to atranslation unit 51 that is structured to impart a controllablemechanical translation to the visual display 62 by a coupling 52. Thecoupling 52 may be comprised of an electromagnetic coupling between thetranslation unit 51 and the display 62, so that no mechanical couplingbetween the translation unit 51 and the display 62 is required.Alternatively, the coupling 52 may be comprised of a mechanical couplingbetween the translation unit 51 and the display 62. The motion impartedto the display 62 may be in a substantially horizontal direction, asindicated by the arrow H, or alternatively in a substantially verticaldirection, as indicated by the arrow V. More generally, however, themotion imparted to the display 62 will consist of some combination ofmotions in the H and V directions. The display 62 is also electricallycoupled to a display signal source 56 that provides input signals to thedisplay 62 through a signal line 57. The source 56 may consist of anydevice capable of providing input signals to a display device, such as adisplay driver attached to a computer, or an analog video signal source.In order to obtain a stable image on the display surface 64, a controlunit 54 is provided to synchronize the display signals (not shown)transferred from the source 56 to the display 62 with the physicaltranslation of the display 62. The control unit 54 is structured totransmit and receive signals to the translation unit 51 through a line53, and to transmit signals to the display signal source 56 through aline 55. The signal line 57, and lines 53 and 55 may be comprised ofelectrical conductors, or alternatively, may consist of wireless signalpaths to permit the translation unit 51, control unit 54, signal source56 and the display device 62 to interact in a wireless manner.

[0032] Referring now to FIG. 6, a schematic view of an apparatus 60 formasking defective display elements according to another embodiment ofthe invention shows a visual display 62 having a frontally disposeddisplay surface 64 positioned within the field of view of a viewer (notshown). The display 62 is coupled to a translation unit 74 that isstructured to impart a controllable mechanical translation to the visualdisplay 62 by a coupling 52. As previously discussed, the coupling 52may be comprised of an electromagnetic coupling between the translationunit 74 and the display 62, or the coupling 52 may be comprised of amechanical coupling between the translation unit 74 and the display 62.The motion imparted to the display 62 may be in a substantiallyhorizontal direction, as indicated by the arrow H, or alternatively in asubstantially vertical direction, as indicated by the arrow V. Moregenerally, however, the motion imparted to the display 62 will consistof some combination of motions in the H and V directions. The display 62is also electrically coupled to a control unit 72 that accepts imagesignals 76 from an image signal source. The source may consist of anydevice capable of providing input signals to a display device, such as adisplay driver attached to a computer, or an analog video signal source.The control unit 72 synchronizes the image signals 76 with the physicaltranslation of the display 62, and is structured to transmit and receivesignals to the translation unit 74 through a line 77, ant to transmitshifted image signals to the display unit 62 through a line 78. Thelines 77 and 78 may be comprised of electrical conductors, oralternatively, may consist of a wireless signal path to permit thetranslation unit 74 and display unit 62 to wirelessly interact with thecontrol unit 72.

[0033] Referring now to FIG. 7, a schematic view of an apparatus 70 formasking defective display elements according to an alternativeembodiment of the invention is shown. As in the previous embodiment, avisual display 62 having a frontally disposed display surface 64 ispositioned within the field of view of a stationary viewer (not shown).The display 62 is constrained to move in the horizontal direction by arelatively low-friction horizontal sliding means 66 that permits thetranslational movement of the device 62 in the x-direction, as shown.The device 62 is further constrained to move in the vertical directionby a similar low-friction vertical sliding means 68, that permits thetranslation of the device 62 in the y-direction, also as shown. Thehorizontal sliding means 66 and the vertical sliding means 68 may allowmovement of the device 62 solely in the x-direction or the y-directionby translating along these directions independently, or, alternatively,the sliding means 66 and 68 may act cooperatively to permit thetranslation of the device 62 in any direction intermediate between the xand y-directions. The horizontal sliding means 66 and vertical slidingmeans 68 may be comprised of linear ball or roller bearings.Alternatively, gas-lubricated linear bearings may also be used, althoughstill other equally acceptable alternatives exist.

[0034] With reference still to FIG. 7, horizontal motion is imparted tothe display 62 by a horizontal actuator 74 that is hingeably attached tothe display 62 by a rotational mount 80. The actuator 74 is alsosimilarly hingeably attached to a stationary, supporting structure 100by rotational mount 88. A vertical actuator 72 that is hingeablyattached to the display 62 by a rotational mount 84, and to thestationary support structure 100 by a rotational mount 94 impartsvertical motion to the display 62. The horizontal actuator 74 andvertical actuator 72 may be separately actuated to impart motion in thex-direction, or the y-direction, respectively. Alternatively, actuators72 and 74 may be actuated simultaneously and cooperatively to imparttranslational motion in a direction intermediate between the x and ydirections. The horizontal actuator 74 and vertical actuator 72 may becomprised of piezoelectric devices that are capable of excitation by asignal generator, although other alternatives exist. For example,electromechanical devices, such as solenoid actuators, may be used, ormechanical devices, such as double-acting pneumatic actuators, may alsobe employed.

[0035] Determination of the position of the display 62 is accomplishedby positional sensors attached to the display 62 that are aligned withthe x and y-directions. The positional information obtained from thesesensors provides feedback information for a closed loop control system,which will be described in more detail below. With reference again toFIG. 7, the horizontal position of the display 62 relative to thestationary support structure is sensed by a horizontal position sensor70 that is hingeably attached to the display 62 by a rotational mount82, and also attached to the support structure 100 by a similarrotational mount 90. A vertical position sensor 76 that has a hingeableattachment to the display 62 by a rotational mount 84, and is alsoattached to the support structure 100 by a rotational mount 92,similarly senses the vertical position of the display 62 relative to thestationary support structure 100. The horizontal position sensor 70 andthe vertical position sensor 76 may be comprised of numerous well-knownelectromechanical devices, such as linear variable differentialtransformers (LVDT), E transformers, or variable capacitance-typedisplacement sensors, although other alternatives exist.

[0036] Still referring to FIG. 7, a computer 300 provides output signalsto a display driver 320 that is electrically coupled to the display 64through a conductor 330. As mentioned earlier, the signals supplied fromthe display driver 320 to the display 64 may provide for raster scanningof the display surface, or alternatively, for the matrix addressing ofdisplay elements on the display surface. The computer 300 is alsoelectrically coupled to a control system 200 through an interface 310,which may provide analog to digital (A/D) or digital to analog (D/A) orany other required processes that allow the computer 300 to communicatewith the control system 200.

[0037] A control system 200 that is capable of receiving positionalinput signals from the position sensors 70 and 76 through the conductors220 and 230 is provided as shown in FIG. 7. The input signalstransmitted to the control system 200 provide a continuous feedback loopfor the system 200. The control system 200 also provides positionaloutput signals to the actuators 72 and 74 through the conductors 240 and210 to properly position the display 62 in response to the detectedposition. Although the control system 200 may employ any of thewell-known control algorithms, a proportional-integral-differentialalgorithm is used.

[0038] The above description of illustrated embodiments of the inventionis not intended to be exhaustive or to limit the invention to theprecise form disclosed. While specific embodiments of, and examples of,the invention are described in the foregoing for illustrative purposes,various equivalent modifications are possible within the scope theinvention, as those skilled in the relevant art will recognize. Forexample, optical sensors to sense the position of the surface by opticalmeans may replace the electromechanical position sensors attached to thedisplay. Further, the control system as described herein may in certaincases be replaced with a synchronizing device to achieve imagestability. Moreover, it will be further appreciated that the imagesdisplayed by the display may be static images, or images from materialhaving motion, such as animation, video, and the like. Still further,the various embodiments described above can be combined to provide stillother embodiments. Accordingly, the invention is not limited by thedisclosure, but instead the scope of the invention is to be determinedentirely by the following claims.

What is claimed is:
 1. An apparatus for masking defects in a visualdisplay, comprising: a visual display unit having a plurality of displayelements; a translation unit coupled to the visual display unit that isstructured to impart motion to the display unit; and a control unitcoupled to the translation unit and the display device that isstructured to receive image signals from an image signal source andcapable of exchanging signals with the translation unit and the displayunit to controllably direct the movement of the display unit and tocompensatingly shift the image signals, the shifted signals concealingdisplay element defects on the display surface.
 2. The apparatusaccording to claim 1, wherein the translation unit imparts motion to thevisual display unit in at least a first direction and a seconddirection, the second direction being substantially perpendicular to thefirst direction.
 3. The apparatus according to claim 2, wherein thetranslation unit imparts a motion primarily in the first direction. 4.The apparatus according to claim 2, wherein the translation unit impartsa motion primarily in the second direction.
 5. The apparatus accordingto claim 1, wherein the translation unit is mechanically coupled to thevisual display unit.
 6. The apparatus according to claim 1, wherein thetranslation unit is electromagnetically coupled to the visual displayunit.
 7. The apparatus according to claim 1, wherein the image signalsource is a display driver attached to a computer.
 8. The apparatusaccording to claim 1, wherein the image signal source is a video signalsource.
 9. The apparatus according to claim 1, wherein the visualdisplay unit is further comprised of a field emission display.
 10. Theapparatus according to claim 1, wherein the visual display unit isfurther comprised of an active matrix liquid crystal display.
 11. Theapparatus according to claim 1, wherein the visual display unit isfurther comprised of a cathode ray tube.
 12. An apparatus for maskingdefects in a visual display, comprising: a visual display unit having aplurality of display elements; a translation unit coupled to the visualdisplay unit that is structured to impart motion to the display unit; adisplay signal source capable of providing input signals to the displayelements on the surface of the visual display; and a control unitcoupled to the translation unit and the display signal source that isstructured to exchange signals with the translation unit and the displaysignal source to controllably direct the movement of the display unitand to compensatingly shift the input signals in the signal source, theshifted signals concealing display element defects on the displaysurface when displayed.
 13. The apparatus according to claim 12, whereinthe translation unit imparts motion to the visual display unit in atleast a first direction and a second direction, the second directionbeing substantially perpendicular to the first direction.
 14. Theapparatus according to claim 13, wherein the translation unit imparts amotion substantially in the first direction.
 15. The apparatus accordingto claim 13, wherein the translation unit imparts a motion substantiallyin the second direction.
 16. The apparatus according to claim 12,wherein the translation unit is mechanically coupled to the visualdisplay unit.
 17. The apparatus according to claim 12, wherein thetranslation unit is electromagnetically coupled to the visual displayunit.
 18. The apparatus according to claim 12, wherein the displaysignal source is a display driver attached to a computer.
 19. Theapparatus according to claim 12, wherein the display signal source is avideo signal source.
 20. The apparatus according to claim 12, whereinthe visual display unit is further comprised of a field emissiondisplay.
 21. The apparatus according to claim 12, wherein the visualdisplay unit is further comprised of an active matrix liquid crystaldisplay.
 22. The apparatus according to claim 12, wherein the visualdisplay unit is further comprised of a cathode ray tube.
 23. Anapparatus for masking visual display surface defects, comprising: adisplay device having a viewing surface and a plurality of contiguousdisplay elements disposed thereon, wherein at least one of the displayelements is defective; a signal source unit capable of directing aplurality of image signals to the plurality of display elements on theviewing surface; a translation device coupled to the display device; anda control unit coupled to the signal source unit and the translationunit that is operable to command the translation unit to shift thedisplay in a predetermined direction and to command the signal sourceunit to correspondingly shift the image signals provided to the displaydevice by the signal source unit to compensate for the display deviceshift before displaying the shifted signals, and to command the displaythereof to obtain a stable image that conceals the at least onedefective display element.
 24. The apparatus according to claim 23,wherein the display device is further comprised of a first sliding meansthat constrains movement of the display to movement in a firstdirection, and a second sliding means that constrains movement of thedisplay to movement in a second direction.
 25. The apparatus accordingto claim 24, wherein the display device is further comprised of a thirdsliding means that constrains movement of the display to movement in athird direction, the third direction being approximately perpendicularto the first and second directions.
 26. The apparatus according to claim25, wherein the sliding means are further comprised of linear bearings.27. The apparatus according to claim 25, wherein the sliding means arefurther comprised of linear gas lubricated bearings.
 28. The apparatusaccording to claim 23, wherein the translation device is furthercomprised of a first actuator to impart a first motion to the displaydevice, and a second actuator to impart a second motion to the displaydevice, the second motion being approximately perpendicular to the firstmotion.
 29. The apparatus according to claim 28, wherein the translationdevice is further comprised of a third actuator to impart a third motionto the display device, the third motion being approximatelyperpendicular to the first and second motions.
 30. The apparatusaccording to claim 28, wherein the actuators are further comprised ofpiezoelectric actuators.
 31. The apparatus according to claim 28,wherein the actuators are further comprised of solenoid actuators. 32.The apparatus according to claim 28, wherein the actuators are furthercomprised of pneumatic actuators.
 33. The apparatus according to claim23, wherein the control unit is further comprised of a first positionsensor to sense a first position of the display relative to a firstdirection, and a second position sensor to sense a second position ofthe display relative to a second direction, the second direction beingapproximately perpendicular to the first direction.
 34. The apparatusaccording to claim 33, wherein the control unit is further comprised ofa third position sensor to sense a third position of the displayrelative to a third direction, the third direction being approximatelyperpendicular to the first and second directions.
 35. The apparatusaccording to claim 34, wherein the position sensors are furthercomprised of linear variable differential transformers.
 36. Theapparatus according to claim 34, wherein the position sensors arefurther comprised of variable capacitance displacement sensors.
 37. Theapparatus according to claim 23, wherein the display device is furthercomprised of a field emission display.
 38. The apparatus according toclaim 23, wherein the display device is further comprised of an activematrix liquid crystal display.
 39. The apparatus according to claim 23,wherein the display device is further comprised of a cathode ray tube.40. The apparatus according to claim 23, wherein the control unit isfurther comprised of a closed feedback control loop using aproportional-integral-differential algorithm.
 41. A method forconcealing a defective display element in a visual display surface,comprising: directing an image signal onto a first display elementpositioned in a first display location, the first display element beingat least partially defective; translating a second display element intothe first display location; directing the image signal onto the seconddisplay element while the second display element is in the firstlocation.
 42. The method according to claim 41 further comprising thestep of translating the first display element into the first displaylocation.
 43. The method according to claim 41 further comprising thestep of translating the first display element into a second displaylocation.
 44. The method according to claim 41, wherein the step oftranslating a second display element into the first display locationcomprises moving a second display element into the first location by aseries of rectilinear movements.
 45. The method according to claim 41,wherein the step of translating a second display element into the firstdisplay location comprises moving a second display element into thefirst location by horizontally translating the second display elementinto the first location.
 46. The method according to claim 41, whereinthe step of translating a second display element into the first displaylocation comprises moving a second display element into the firstlocation by vertically translating the second display element into thefirst location.
 47. The method according to claim 41, wherein the stepof translating a second display element into the first display locationcomprises moving a second display element into the first location byhorizontally translating a second display element adjacent to the firstdisplay element into the first location.
 48. The method according toclaim 41, wherein the step of translating a second display element intothe first display location comprises moving a second display elementinto the first location by vertically translating a second displayelement adjacent to the first display element into the first location.49. The method according to claim 41, wherein the steps of directing theimage signals are further comprised of raster scanning the displayelements on the display surface.
 50. The method according to claim 41,wherein the steps of directing the image signals are further comprisedof matrix addressing the display elements on the display surface.